Estimation of velocity profiles in natural channels during high floods

Four different approaches to describe the velocity profile along verticals in natural channels have been investigated. Three methods consider the classical logarithmic law with additional terms, which introduce the dip-phenomenon and the curvature of the velocity profile. The latter uses a modified entropic distribution of velocity profiles. Methods have been tested to reproduce the velocity profile during high flows, when velocity measurements can be carried out only in the upper portion of the flow area. An equipped hydrometric site located along the Po river, in northern Italy, has been used as case study. Four velocity measurements have been selected and the hypothesis of high flood has been considered. The methods reliability has been investigated in terms of percentage errors in estimating both the mean velocity along each sampled vertical and the mean flow velocity. It was found that the entropic approach performed better than the other ones, showing that it can be efficiently applied for high flood conditions.